The present invention improves the power efficiency of systems wherein power is conserved by temporarily reducing the voltage supplied to temporarily unused system components. In addition to reducing voltage, the present invention drains charge from filter and bypasses capacitors, or other load-related capacitance, and returns a substantial fraction thereof to system power sources. Thus, when temporary voltage reductions and subsequent restorations become frequent, the loss of energy associated with repeated charging and discharging of capacitors is substantially reduced.
Many computer systems conserve power by temporarily reducing voltage to temporarily unneeded portions of their circuitry. Usually, computer circuitry is replete with capacitors needed to filter line and load transients. Each time such capacitors are charged, energy is imparted to them. Since most voltage regulators can but unidirectionally pass power, each time a voltage reduction occurs capacitive energy is dissipated by the circuitry without useful work being done. In this case, if the cycling up and down of voltage becomes sufficiently frequent, power saved by voltage reduction is largely consumed by charging and discharging capacitors.
This problem of wasted energy from load capacitance is particularly acute with computer servers and server farms. These devices and networks (which may have hundreds at individual computers) have a lot of energy stored in capacitance. They often shut down for periods of time and this stored energy is dissipated (i.e. wasted).
Likewise similar problems exist in portable electronic devices such as cell phones and lap top computers where it is important to conserve all energy. Power stored in the load capacitors of device is typically not returned to the battery.
There exist numerous prior art inventions for intentionally returning to the source, or otherwise usefully employing, the energy that occurs in snubber capacitors. There also exist other bidirectional forms of power converters such as described in U.S. Pat. No. 7,348,767 to Hack et al. The novelty of the current invention lies in the use for of a bidirectional converter for the recovery of capacitive energy stored in the filter and load capacitance. In Hack, bidirectional power flow to and from a reactor is taught, however that reactor in Hack is an inductor internal to the power converter itself, necessary for its power-converting function, and no recovery of energy from a substantially reactive load is taught.